Investigations on the stimulated Brillouin scattering reflectivity by FC-72 medium and the beam recombination using stimulated Brillouin scattering phase conjugation mirror were performed in this paper.
Stimulated Brillouin scattering is the light scattering due to the density fluctuation of the medium produced by optically induced electrostriction forces. The characteristics of stimulated Brillouin scattering are phase conjugation mirror effect, pulse compression effect, beam smoothing effect, and etc.. By these effects, stimulated Brillouin scattering can be applied to increase the efficiency of the high-power solid-state laser system.
To use stimulated Brillouin scattering in high power laser system, several limitations should be overcome. Low reflectivity, low break down threshold are the major limitations.
In this experiment FC-72 is used as stimulated Brillouin scattering medium and the purification system up to 0.2㎛ filtering is applied to higher the reflectivity and the break down threshold.
As a result, the reflectivity can be obtained up to 96% of the input beam energy. The break down threshold is increased to 180 mJ which was around 60 mJ without purification. Simulation shows the close tendency of increasing reflectivity relative to input energy.
Also, the beam recombination experiment is performed. Beam recombination is the way of achieving high power, high repetition solid state laser. To do this, we divide the wave front of the input beam using square type wedges. And each divided beams were amplified and recombined using stimulated Brillouin scattering phase conjugation mirror.
The spatial profiles of the recombined beam is almost the same as input beam profile which means stimulated Brillouin scattering phase conjugation effect performs well. But if we use the ordinary mirror instead, the spatial profile of the recombined beam is distorted due to the diffraction effect by wedges.
In the recombined beam spatial profile, the gap is shown between each beams. This gap was investigated by simulation. The result of simulation showed that the gap is mainly due to the phase difference between two returned beams.
